| |
Valve is a device that regulates the flow of
substances (either gases, fluidized solids,
slurries, or liquids) by opening, closing, or
partially obstructing various passageways. Valves
are technically pipe fittings, but usually are
discussed separately. Valves are used in a variety
of applications including industrial, military,
commercial, residential, and transportation. Oil &
Gas, Power Generation, Mining, Water Reticulation,
Sewerage & Chemical Manufacturing would constitute
the majority of valves used by industry. Plumbing
valves are the most obvious in everyday life, taps
for hot and cold water, gas control valves on
cookers and barbecues, small valves fitted to
washing machines and dishwashers, safety devices
fitted to hot water systems are all simple valves.
Most valves are operated manually, either by a hand
wheel or lever. Some valves are 'self operating'
driven by changes in pressure, temperature or flow.
These changes in pressure or temperature often act
against springs or capsules filled with expanding
substances. Examples of this type of valve found
commonly are safety valves fitted to hot water
systems or steam boilers. Valves are also found in
the Otto cycle (internal combustion) engines driven
by a camshaft, lifters and or push rods where they
play a major role in engine cycle control.
Applications
A huge variety of valves are available and have
infinite applications with sizes ranging from 1/4"
(6mm) to 24" (600mm) Special valves can be
manufactured to be in excess of 200" (5000mm)
diameter.
Valves range from inexpensive, simple, disposable
valves to items in exotic materials that in some
instances cost thousands of dollars (US$) per inch
(25mm) of diameter. These items would only be used
on specialized extreme applications.
Disposable valves are inside some common household
items including liquid or gel mini-pump dispensers,
aerosol spray devices, some rubber bulbs for pumping
air etc.
Types/Designations
Valves can be categorized into the following design
types and although there are hundreds of variations
they all fit into these basic types:
Gate, Plug, Globe, Check, Butterfly, Diaphragm &
Ball. |
